You will likely have to, and more; afaict, your bike has at least two separate problems, plus you have introduced at least one other:-
These are both wrong:-
. A T140
E was originally fitted with Champion N
5 plugs. NGK B
8ES is the equivalent of Champion N
3 fitted to earlier Triumphs.
. ND W31ES are equivalent to a NGK
10 heat range so you've gone in completely the wrong direction, much too 'cold' for a standard engine.
If your bike's engine is standard, if not Champion N5, you require NGK B
6ES or ND equivalent.
As primary and crankcase are connected in your bike's engine, you need to establish whether the something in the primary is the source of the metal in the oil, or the source is somewhere else in the engine.
Know that another reason for "metal bits in the oil" that do not stick to a magnet is the big-end bearings are in the process of destroying themselves. Basically, an oil pressure gauge connected in place of the warning switch in the timing cover will tell you if the oil pressure figures are what the workshop manual says they should be. However, any pressure gauge gauge fitted must have:-
. a 1/8"NPT (National Pipe Tapered) or NPS (National Pipe Straight) male thread - the timing cover is threaded NPS but NPT is more common;
. a flexible hose between male thread and gauge - you will need to be able to ride the bike to warm the engine
thoroughly, the workshop manual pressures are for hot oil, cold oil pressures are higher; you will need to mount the gauge where you can see it when riding.
"the aluminum in oil problem" is unlikely to be caused by "metal specs on the top of both intake valves and pitting of both pistons", the latter is most likely caused by pre-ignition or detonation. While this
might be a "lean ... condition" caused by the "glasspack mufflers" reducing exhaust back pressure, it can also be caused simply by the way some owners ride their old Triumphs.
Regrettably, the combustion chamber is a poor shape for modern fuel and, especially if large throttle openings are used at relatively low engine rpm, it's relatively easy to induce especially detonation even if both induction and exhaust are standard.
Assuming the needle clip is in the in the needle's centre groove, the "Current carb set up" is about standard - that the pilot jet is smaller than original (it should be #25) is unlikely to be a factor in either pre-ignition or detonation. However, if you are trying to cure a "lean fuel condition", why would you fiddle with the needle and needle jet without either checking for excessive wear or mentioning the main jet? Read any Amal tuning guide and you always fix the main jet first.
However, as your bike "has 24k miles on it", first thing I'd be checking for is excessive clearance between slides and bodies. Slides are replaceable so only worn bodies would be a reason for splashing out on brand-new carbs.
If slide-body clearances are within spec., next I'd replace needle jets (wearing items) and possibly needles, but with standard. If you believe you might want to test for a richer mixture because of the mufflers, add a pair of 220 main jets to your Amal order.
Because Amal suffers badly with fake parts sold online, buy either direct from Amal or, at worst, from a long-time bricks-'n'-mortar spares dealer.